Question

The xylem in which the protoxylem is directed towards the periphery and metaxylem towards the center
(a) Exarch
(b) Mesarch
(c) Endarch
(d) Diarch

Answer 1

Hint: Complex tissues are made up of more than one type of cell. The type of xylem found in the parts of the plant which helps in the absorption of nutrients from the soil as well as acts as an anchorage where the xylem develops from the outward to the inward direction.

Complete answer:
Xylem is the chief water-conducting tissue of the plants.
The Exarch condition of xylem is present in which the metaxylem lies towards the center and the protoxylem towards the periphery. This condition is found in the roots of the plants.

Additional Information: The xylem which arises early, i.e., during the primary growth of the plant body is called the primary xylem. There are also two forms, Protoxylem and Metaxylem, based on their roots.
-The first formed xylem is known as protoxylem and the later formed is known as metaxylem.
-The arrangement of primary xylem occurs in two ways, Exarch and Endarch.
-In the endarch condition, the protoxylem (the first-formed xylem) lies towards the center (pith) and the metaxylem (the later-formed xylem) lies towards the periphery. Hence, the youngest lies closest to the periphery in this type of arrangement.
-In exarch condition, the protoxylem (the first-formed xylem) lies towards the periphery and the metaxylem (the later-formed xylem) lies towards the center (pith). Hence, the youngest lies closest to the center in this type of arrangement.
So, the answer is, “Exarch.”

Note: -The metaxylem is more mature than the protoxylem.
- Protoxylem has narrow-lumen vessels, and metaxylem has broad-diameter vessels.
-Endarch type of arrangement occurs in stems whereas the exarch condition occurs in the roots.